1. Field of the Invention
The invention relates to an improved self-boosting vehicle brake.
2. Description of the Prior Art
One vehicle brake in the form of a disk brake known, from German Published Patent Disclosure DE 102 01 555 A1, has a brake disk which is braked by means of a friction brake lining and an actuating device with which the friction brake lining can be pressed against the brake disk that forms the brake body. The known vehicle brake furthermore has a self-boosting device, which when the brake is actuated converts a frictional force, exerted by the rotating brake body onto the friction brake lining pressed against it, into a contact pressure, which, in addition to a contact pressure exerted by the actuating device, presses the friction brake lining against the brake body and as a result boosts the braking force of the vehicle brake.
The self-boosting device of the known vehicle brake has a wedge mechanism, which guides the friction brake lining displaceably at an angle and in the circumferential direction to the brake disk. The bracing of the friction brake lining on a wedge face, extending at an angle to the brake disk, brings about the additional contact pressure on the principle of a wedge and thus brings about the braking force boosting. To attain self-boosting for both directions of rotation of the brake disk, the vehicle brake can have two wedge faces, extending oppositely to one another or in pairs obliquely to the brake disk, whose slope need not necessarily be the same. The wedge angle may also vary over the length of the wedge face, particularly in order at the onset of the actuation to attain a long positioning distance and a high positioning speed of the friction brake lining and at the end of the displacement of the friction brake lining, at a high braking force, to attain high self-boosting. In that case, the term ramp mechanism is used.
The self-boosting device is intended in particular for a disk brake, but in principle it can be used for other forms of brakes as well, such as a drum brake. In that case, the brake body is a brake drum.
With the wedge mechanism, the known vehicle brake has a mechanical self-boosting device; other mechanical self-boosting devices are possible and are known, such as support lever constructions that brace the friction brake lining at a support angle to the brake disk. The support angle corresponds to the wedge angle; it is a mechanical analogue. Still other self-boosting devices, for instance hydraulic ones, are known and are possible.
When high self-boosting actions are sought, the problem of self-locking arises; the vehicle brake can lock. To protect against locking, the actuating device of the known vehicle brake is embodied as self-locking against an independent motion of the friction brake lining; the friction brake lining can be moved only with the actuating device. As a result, the braking force of the actuated vehicle brake does not increase independently from the self-boosting; instead, the braking force can be changed only with the actuating device.
Another known disk brake, also mechanically self-boosting by means of a wedge mechanism, is known from German Patent DE 101 56 348 C1. In this disk brake, two contrarily acting actuating devices are provided, which keep the friction brake lining free of play and prevent a displacement of the friction brake lining and hence any change in the braking force from the friction between the rotating brake disk and the brake body pressed against it when the disk brake has been actuated.